Modified oilseed materials are used as food additives for enhancing texture and other functional characteristics of various food products as well as a source of protein. The use of modified oilseed materials particularly modified soybean materials may be limited in some instances, however, due to their beany flavor and tan-like color. It is still unclear exactly which components are responsible for the flavor and color characteristics of oilseeds, though a variety of compounds are suspected of causing these characteristics. Among these are aliphatic carbonyls, phenolics, volatile fatty acids and amines, esters and alcohols.
There are extensive reports of processes used for the isolation, purification and improvement of the nutritional quality and flavor of oilseed materials, particularly soybean materials. Soybean protein in its native state is unpalatable and has impaired nutritional quality due to the presence of phytic acid complexes which interfere with mammalian mineral absorption, and the presence of antinutritional factors which interfere with protein digestion in mammals. The reported methods include the destruction of the trypsin inhibitors by heat treatment as well as methods for the removal of phytic acid. A wide variety of attempts to improve the yield of protein secured as purified isolate relative to that contained in the soybean raw material have also been described.
Many processes for improving soy protein flavor involve the application of heat, toasting, alcohol extraction and/or enzyme modification. These types of processes often result in substantial protein denaturation and modification, thereby substantially altering the product""s functionality. In addition, these processes can promote interactions between proteins with lipid and carbohydrate constituents and their decomposition products. These types of reactions can reduce the utility of soy proteins in food products, especially in those that require highly soluble and functional proteins, as in dairy foods and beverages.
Commercial soy protein concentrates, which are defined as soy protein products having at least 70% by weight protein (dry solids basis or xe2x80x9cdsbxe2x80x9d), are generally produced by removing soluble sugars, ash and some minor constituents. The sugars are commonly removed by extracting with: (1) aqueous alcohol; (2) dilute aqueous acid; or (3) water, after first insolubilizing the protein with moist heating. These processes generally produce soy protein products with a distinctive taste and color.
Soy protein isolates are defined as products having at least 90% by weight protein (dsb). Commercial processes for producing soy protein isolates are generally based on acid precipitation of protein. These methods of producing, typically include (1) extracting the protein from soy flakes with water at an alkaline pH and removing solids from the liquid extract; (2) subjecting the liquid extract to isoelectric precipitation by adjusting the pH of the liquid extract to the point of minimum protein solubility to obtain the maximum amount of protein precipitate; and (3) separating precipitated protein curd from by-product liquid whey. This type of process, however, still tends to produce a protein product with a distinctive taste and color.
A number of examples of processes for producing concentrated soy protein products using membrane filtration technology have been reported. Due to a number of factors including cost, efficiency and/or product characteristics, however, membrane-based purification approaches have never experienced widespread adoption as commercial processes. These processes can suffer from one or more disadvantages, such as reduced functional characteristics in the resulting protein product and/or the production of a product which has an xe2x80x9coffxe2x80x9d flavor and/or an off-color such as a dark cream to light tan color. Membrane-based processes can also be difficult to operate under commercial production conditions due to problems associated with bacterial contamination and fouling of the membranes. Bacterial contamination can have undesirable consequences for the flavor of the product.
Frozen dessert compositions which include modified oilseed material with desirable flavor and/or color characteristics derived from oilseed material, such as defatted soybean white flakes or soybean meal, are described herein. The present frozen dessert products, which include the modified oilseed material are particularly suitable for use as a protein source for human and/or animal consumption.
The present modified oilseed material can be produced by a membrane-based purification process which typically includes an extraction step to solubolize proteinaceous material present in an oilseed material. It may be desirable to conduct the extraction as a continuous, multistage process, e.g., a countercurrent extraction.
The modified oilseed material can commonly be produced by a process which includes an extraction step to solubilize proteinaceous material present in an oilseed material. The process uses one or more microporous membranes to separate and concentrate protein from the extract. It is generally advantageous to use a microporous membrane which has a filter surface with a relatively low contact angle, e.g., no more than about 40 degrees. The process commonly utilizes either relatively large pore ultrafiltration membranes (e.g., membranes with a molecular weight cut-off (xe2x80x9cMWCOxe2x80x9d) of about 25,000 to 500,000) or microfiltration membranes with pore sizes up to about 1.5xcexc. When microfiltration membranes are employed, those with pore sizes of no more than about 1.0xcexc and, more desirably, no more than about 0.5xcexc are particularly suitable. Herein, the term xe2x80x9cmicroporous membranexe2x80x9d is used to refer to ultrafiltration membranes and microfiltration membranes collectively. By employing such relatively large pore microporous membranes, the membrane filtration operation in the present process can be carried out using transmembrane pressures of no more than about 100 psig, desirably no more than about 50 psig, and more commonly in the range of 10-20 psig.
The modified oilseed material formed by the present method can be used to produce protein supplemented food products such as frozen dessert products. The modified oilseed material can have a variety of characteristics that make it suitable for use as a protein source for incorporation into food products. A suitable modified oilseed material may include at least about 85 wt. % (dsb) protein, preferably at least about 90 wt. % (dsb) protein, and have one or more of the following characteristics: a MW50 of at least about 200 kDa; at least about 40% of the material has an apparent molecular weight of greater than 300 kDa; at least about 40 wt. % of the protein in a 50 mg sample may be soluable in 1.0 mL water at 25xc2x0 C.; a turbidity factor of no more than about 0.95; a 13.5% aqueous solution forms a gel having a breaking strength of no more than about 25 g; an NSI of at least about 80; at least about 1.4% cysteine as a percentage of total protein; a Gardner L value of at least about 85; a substantially bland taste; a viscosity slope of at least about 10 cP/min; an EOR of no more than about 0.75 mL; a melting temperature of at least about 87xc2x0 C.; a latent heat of at least about 5 joules/g; a ratio of sodium ions to a total amount of sodium, calcium and potassium ions of no more than 0.5; no more than about 7000 mg/kg (dsb) sodium ions; and a bacteria load of no more than about 50,000 cfu/g.
A particularly desirable modified oilseed material formed by the present method which may be used to produce a protein supplemented food product may include at least about 85 wt. % (dsb) protein, preferably at least about 90 wt. % (dsb) protein, and meet one or more of the following criteria: a MW50 of at least about 400 kDa; at least about 60% of the material has an apparent molecular weight of greater than 300 kDa; at least about 40 wt. % of the protein in a 50 mg sample may be soluable in 1.0 mL water at 25xc2x0 C.; a turbidity factor of no more than about 0.95; a 13.5% aqueous solution forms a gel having a breaking strength of no more than about 25 g; an NSI of at least about 80; at least about 1.5% cysteine as a percentage of total protein; a Gardner L value of at least about 85; a substantially bland taste; a viscosity slope of at least about 50 cP/min; an EOR of no more than about 0.5 mL; a melting temperature of at least about 87xc2x0 C.; a latent heat of at least about 5 joules/g; a ratio of sodium ions to a total amount of sodium, calcium and potassium ions of no more than 0.5; no more than about 7000 mg/kg (dsb) sodium ions; and a bacteria load of no more than about 50,000 cfu/g.